Refractometer



June 15, 1937. J, W FQRREST 2,083,778

REFRAGTOMETER Filed Jan. 18, 1935 INVENTOR .BY/@ MQML ATTORNEY Patented June 1,5', 1937 UNITED STATES *PATENT OFFICE vBausch & Lomb Optical Company, Rochester,

N. Y., a corporation of New York Application January 18, 1935, lSerial No. '2,386

6 Claims.

The present invention relates to refractometers and has particular reference to dipping refractometers for measuring the index of refraction of liquids.

In the manufacture of dipping refractometers, it has heretofore been the practice to x the `dipping prism in the end of the telescope tube and the fluid chamber, a metal cup with a transparent bottom, is detachably connected to the telescope tube over the dipping prism. In order to get the fluid at the desired temperature, the fluid chamber and prism are then immersed in -a water bath with the hypotenuse of the prism facing downwardly. The temperature of the Water bath is then measured and the fluid is assumed to be at the-same temperature.

This system has certain inherent disadvantages. It is almost impossible to obtain a fluid tight joint between the transparent cup fluid 0 chamber and the refractcmeter body and hence there is always the danger of dilution of the fluid by the ywater of the bath. Another disadvantage liesin the fact that the cup is removable. The `outer end of the dipping prism tapers to a ne edge and this edge is frequently broken during the putting on or removal of the cup. The glass and metal cup is unsuitable as a fluid chamber due to its low thermal conductivity and the temperature reading taken in the water bath may or may not be the temperature of the fluid. Still another disadvantage is that the prism faces downwardly. In this position air bubbles will rise to the face of the prism and cause errors in the reading. The fact that the illuminating beam must pass through the water of the bath is another disadvantage.

1 The present invention has for an object the provision of a new and improved refractometer for uids. Another object is to provide a new and improved fluid chamber for a refractometer.

A further object is to provide a dipping refractometer in which the prism is fixed in the fluid chamber. A further object is to provide a refractometer fluid chamber having high thermal conductivity. Still another object is to provide a fluid chamber having a water jacket. A still further object is to provide a refractometer fluid chamber in which the temperature of the fluid is measured at a point adjacent the prism face. A further object is to provide a refractometer in whichthe prism faces upwardly. These and other objects and advantages reside in certain novel features of construction, arrangement and com- 55 bination of parts as will hereinafter be more fully set forth and pointed out in the appended claims.

Referring to the drawing: Fig. 1 is a side elevation of a dipping refractometer embodying my invention and 5 Fig. 2 is an enlarged vertical section of my improved fluid chamber. 'n

One embodiment of this invention is illustrated in the drawing wherein I 0 indicates a refractometer base pivotally supporting a bracket II carrying a lamp house I2 and a telescope I3. 'The fluid chamber assembly indicated vgenerally at Iii is mounted onthe end `of the telescope I3. AThe bracket II has two arms II'and I3' which support the telescope I3 at the center of weight and adjacent the eyepiece respectively.

The fluid chamber I5 has a tubular wall I6 of metal of high thermal conductivity such as lcopper and this wall is roughened on both sides to increase its surface area. An outwardly ex- 20 tending annular ring I'I is sweatedover one end of the wa-ll I6 and a second wall I8 of polished metal of low thermal Vconductivity such as Ibrass is sweated over the outersurface of the ring' I'I parallel to the wall I6. A second annular ring I9 25 is sweated on to both the wall I6 and the wall I8 enclosing a chamber 20 completely surrounding the fluid chamber I5. The end of the fluid chamber I5 adjacent the annular ring II is closed by a glass plate 2I and a diaphragm 2| which are held in position by a retaining member or nut 22 threaded into the wall I8.

The annular ring I3 has a threaded portion 23 for engaging the telescope I4 and is held in adjusted position by a set screw 24. The dipping prism 25 is cemented or otherwise fixed in the ring I9 so as to extend into the chamber I5 with its hypotenuse facing upwardly. The prism 25 is formed with a shoulder 26 and the joint between the prism 25 and the ring I9 forms a. fluid tight closure for the other end of the chamber I5.

The fluid to be measured is introduced into the chamber through a tap 2T leading to the chamber I5 through a bore 28 in the ring I'I. The ring I9 -has a bore 29 opening into the chamber I5 and an outlet 30 under the control, of a Valve 3| is secured in the bore 29. Two taps 32 and 33 open into the water jacket 2U to form respectively an inlet and an outlet for the heating or cooling water. The ring II has a second bore 34 through which a thermometer 35 extends into the chamber I5 to a point adjacent the hypotenuse face of the prism 25.

In the refining of sugar the concentration of the sugar solution can be determined from the index of refraction of the solution. With the present apparatus it is easy and simple to determine the index of refraction of such a solution. 'I'he chamber l5 is filled through the tap 21 and the solution passes through the annular ring I1 thus avoiding the necessity of a soldered tube. The solution is then brought to the desired temperature by passing water through the water jacket and this temperature is measured by the thermometer 35 adjacent the face of the prism 25. By introducing the solution below the prism away from its hypotenuse, no air bubbles will form on the hypotenuse face to interfere with the readings. The chamber I5 is emptied through the outlet 3U.

From the foregoing it will be apparent that I am able to attain the objects of my invention and provide a new and improved dipping refractometer having a more accurate temperature indicating system, in which the dipping prism is protected against damage and in which the illumination is greatly improve-d. Various modications can, of course, be made without departing from the spirit of my invention or the scope of the appended claims.

I claim:

1. A refractometer comprising a fluid chamber, va window closing one end of said chamber, an annular ring secured at the other end of said Achamber with its central opening substantially concentric with said chamber, a dipping prism secured in and closing said opening and extending into said chamber, a threaded portion on said ring concentric with said opening, a telescope threaded in said portion, and inlet and outlet means for admitting and removing fluid from A said chamber.

2. In a refractometer, a fluid chamber having a fluid outlet, a Window closing one end of said chamber,a diaphragm covering said window and having a small opening adjacent one wall of the chamber, an annular ring secured in the other end of the chamber with its central opening substantially concentric with said chamber, a dipping prism secured in and closing said opening and extending longitudinally into said chamber with its edge adjacent the opening in said diaphragm, a threaded portion on said ring concentric with said opening, a telescope threaded in said portion, and inlet and outlet means for admitting and removing fluid from said chamber.

3. In a refractometer a uid chamber, a jacket surrounding said chamber, a ring extending between said jacket and said chamber for sealing said jacket and a dipping prism xed in said ring and extending into said chamber.

4. In a refractometer a fluid chamber, a. dipping prism fixed in said chamber, a wall surrounding said chamber to form a Water jacket, a sealing ring extending between said chamber and said wall and a thermometer extending through said ring into said chamber to a point adjacent the face of said prism.

5. A fluid chamber for a refractometer comprising a wall of high thermal conductivity forming a chamber, a second wall surrounding said rst wall and spaced therefrom to form a water jacket, a transparent Window sealing one end of said chamber, a wall closing the other end of said chamber and a dipping prism xedly mounted in said wall and extending into said chamber.

6. In a refractometer a uid chamber having rough Walls of high thermal conductivity, a water jacket surrounding said chamber having smooth walls of low thermal conductivity, a. ring'for sealing one end of said jacket extending between said walls, a uid inlet opening into said chamber through said ring, a temperature indicating device extending into said chamber through said ring, a second ring for sealing the other end of said jacket, an outlet for said chamber extending through said second ring, a dipping prism and means for securing a dipping prism in said second ring to seal said chamber.

JOHN W. FORREST. 

